THE EDGE OF THE YOUNG GALACTIC DISK
THE EDGE OF THE YOUNG GALACTIC DISK
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DOI：
10.1088/0004-637x/718/2/683
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
G. Carraro;R. Vazquez;E. Costa;Gabriel I. Perren;A. Moitinho
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文献类型：
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作者：
G. Carraro;R. Vazquez;E. Costa;Gabriel I. Perren;A. Moitinho
在这项工作中，我们报告和讨论的两个遥远的弥漫恒星集团在银河系第三象限的检测。它们由年轻的恒星组成，光谱类型从晚O到晚B，距离在15到20 kpc之间。这两个星团位于两个星表中的疏散星团（VdB-Hagen 04和Ruprecht 30）的区域，投射到船帆座-船尾座星座，并位于大犬座的核心。通过分析它们的颜色-颜色和颜色-星等图，估计了它们的红化和距离，这些图来自深UBV测光。年轻的星星聚集体存在于离银河系中心如此极端的距离上，这挑战了人们普遍接受的观点，即银河系盘在离银河系中心约14千秒差距处有一个尖锐的截止点，这表明它延伸到更远的距离上（最近探测到的CO分子复合体也支持这一观点）。虽然我们在鲁普雷希特30区域发现的星系群分别与猎户座和诺玛-天鹅座旋臂相匹配，但我们在VdB-Hagen 04区域发现的遥远星系群位于诺玛-天鹅座旋臂的外部区域，在银河系中心距离（120 kpc）处，迄今为止在光学上没有发现年轻恒星。
In this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20 kpc. These groups are located in the area of two cataloged open clusters (VdB–Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color–color and color–magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14 kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB–Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance (∼20 kpc) where no young stars have been detected so far in the optical.